The basic purpose of the present study is to determine the ability of peptic ulcer patients to voluntarily control their gastric acid secretions through biofeedback of gastric pH. The four objectives of the study include 1) to determine the effect of prolonged training on the ability of peptic ulcer patients to voluntarily reduce and control their own gastric acid secretions, 2) to determine the suggestive effect of the instructional set independent of biofeedback on reducing high acid secretion; 3) to determine the effect of withdrawing biofeedback following prolonged training on subject's (S's) ability to rely on his own unamplified body cues in gastric acid control; and 4) to study the effect of (CNS mediated) striated stomach muscle tension and (ANS mediated) smooth muscle motility changes on the production of hydrochloric acid secretions. Sixty duodenal ulcer Ss will receive twenty training sessions in the long term control of stomach acid pH. Stomach acid pH will be continuously monitored and displayed visually and auditorily to the S to provide immediate reinforcement of pH changes. One group will be given biofeedback plus clear instructions about the nature of the task. A second group will test the effects of biofeedback alone by reducing the amount of information given about the purpose of the task. A third group, given complete instructions and biofeedback, will have feedback withdrawn on alternate training sessions during the second 10 weeks to determine if Ss can learn to control their own body functions without biofeedback equipment. A fourth group will control for the effects of any (random) feedback on gastric acid control.